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I failed smog. Heated O2 wiring questions now.

If you wanted to take a road trip, I know a guy who charges 150 for smog. He'll make that sub run as clean as a 98 honda civic for the time its on the dyno.
 
I have a guy here that will do it for $200.00, but it's a newly installed rebuilt motor. Stock!!!! I figured it should pass because it stock. If I knew it would have been like this, I would have just paid the $200.00. I Want it to run right though.



Thanks though!:waytogo:
 
You would be surprised at how "bad" mechanics have to make them run to get through the sniffer sometimes... Its crazy. Sometimes have to make the run horrible to get them to PASS!! Never really understood it but when i was mechanicing we did that alot. Make them run like poop, they pass, bring them back and make them run good again.
 
Making the engines run bad to pass emissions is usually a carb'd thing, I remember my dad doing that with our old 6 cyl Nova, lean out the carb to where it runs like crap with low power, passes with flying colors, he had it running so lean once, they tested it twice to be sure, co2 reading was like .10

With yours being a stock rebuild, and all computer controlled, I would really say something in the system is not working or reading what the engine is doing properly, causing a rich condition. I don't have a heated O2 sensor in my Burn with the long tube headers, and do get a check engine light quite often with it. Had it registered out of an emission regulated county, so I don't know what the readings are when it does it. Mine is also a fairly stock rebuild with the exception of roller cam & lifters.

Check for codes, replace the o2 sensor, see what it does.
 
I pulled the codes and none showed up.



Anybody have a part number for the heated O2 or what rig they are for?


Thanks!
 
AFS-74, Delco heated three wire O2. Not as expensive as you might think.

Bosch O2 sensors are generally maligned in GM circles as not working very well. That said, I've got one on my truck, as does my Dad, and thus far they are working fine. Mine is ~10 years old.

Really should start datalogging/scanning that thing to see what is going on. I'm no pro, but if the O2 is switching rich/lean going down the freeway, the O2 sensor likely isn't bad.

Cable from moates.net or ebay is probably $60 or less, if you've got a laptop you can SEE what all the sensors are "telling" the ECM. Cheaper than replacing a variety of sensors.
 
How would I hook this up? My plug looks nothing like this.
I will have a party at my house when this passes. I will be flying everyone to my house!







 
dyeager535 said:
AFS-74, Delco heated three wire O2. Not as expensive as you might think.

Bosch O2 sensors are generally maligned in GM circles as not working very well. That said, I've got one on my truck, as does my Dad, and thus far they are working fine. Mine is ~10 years old.

Really should start datalogging/scanning that thing to see what is going on. I'm no pro, but if the O2 is switching rich/lean going down the freeway, the O2 sensor likely isn't bad.

Cable from moates.net or ebay is probably $60 or less, if you've got a laptop you can SEE what all the sensors are "telling" the ECM. Cheaper than replacing a variety of sensors.
Click to expand...



I ordered that o2 sensor, and the following plug from Rock Auto. I spent a bunch of time verifying i got the right plug, and it showed up and fits. Now i just need to install it

1994 CHEVROLET BLAZER 5.7L V8
ACDELCOAFS74 Oxygen Sensor $ 49.79
ACDELCOPT643 Oxygen Sensor Connector$24.79


So.....i'd order these parts.

Now, hijack question, but helpful to you too:

What wires get power/ground/signal?

Is 12v ok, or does it need to be stepped down? I've read both.
 
Darn, browser crashed, lost post.

I have never heard of it needing to be stepped down. My Dad has been running it on 12V ignition for months if not longer, no problems. All wiring references online I've seen show 12V.

Apparently these are coming with different color wires, but two of the wires should be same color, and those are your power/ground wires. Doesn't matter which gets which. Remaining wire (purple?) is the signal wire. Fuse the power wire of course, no idea what amp it would need, probably very small.

This connector seems pretty reasonable, since it has a single weatherpack for signal http://www.casperselectronics.com/store2/product_info.php?products_id=1068

Unfortunately the AFS-74 was pretty limited in application, so wrecking yards aren't a great source for that plug. Plugs/pigtails are so expensive.
 
dyeager535 said:
Darn, browser crashed, lost post.

I have never heard of it needing to be stepped down. My Dad has been running it on 12V ignition for months if not longer, no problems. All wiring references online I've seen show 12V.

Apparently these are coming with different color wires, but two of the wires should be same color, and those are your power/ground wires. Doesn't matter which gets which. Remaining wire (purple?) is the signal wire. Fuse the power wire of course, no idea what amp it would need, probably very small.

This connector seems pretty reasonable, since it has a single weatherpack for signal http://www.casperselectronics.com/store2/product_info.php?products_id=1068

Unfortunately the AFS-74 was pretty limited in application, so wrecking yards aren't a great source for that plug. Plugs/pigtails are so expensive.
Click to expand...

The AC Delco plug was expensive, but at least it fits. Really, not worth my time right now to find it cheaper, but that Grand National one would have been perfect! All hte AC delco plug wires are white.....but i can figure out which is signal on the GN plug link you sent.

THanks!
 
Man, they are really getting cheap if all wires are the same color now. I suppose they don't think about retrofitters when they build these things.

As you said, based on the plug pinout, should be easy to determine which is signal.
 
If you measure the resistance between all three wires would only two give a reading of some sort for the heating element?
 
You wouldn't measure resistance on the O2 signal wire itself, I have seen it mentioned you can heat up the element with a torch (not crazy hot of course) and check for output voltage. The sensor generates voltage, it's not like a temp sensor that uses a reference signal (IE 5V in, how much comes out) where you would check resistance.

Measuring resistance on the signal wire, it is possible to damage the sensor.
 
rampage said:
If you measure the resistance between all three wires would only two give a reading of some sort for the heating element?
Click to expand...


I guess you could measure continuity, and pick the connection of 2 with the least resistance. But really, no need to do that, its easy enough to find pin-outs online.

I don't guess on $50 sensors....unless i can return them to the local kragen:haha:
 
Got my 3 wire all hooked up. Haven't' put enough miles on it to see if its working, but we'll see!

So here's a question. Does a 3 wire function like a 1 wire if no power is provided to it? Meaning, will it still read and provide a signal back to the computer....or does it HAVE to have that power?

I ask, because currently, mine is wired to a spare ACC ign on feed under my hood. This is all fine and dandy when the truck is running with the key in....but if i remote start it, this circuit doesn't get power.

I need to transfer the power to actual IGN power, but didn't have time.
 
I have never actually seen a schematic on one, but as I understand it, the extra wire(s) are simply a heater.
They make sure the sensor is up to operating temperature quickly and at all times.

So you can just think of it as a regular sensor with a heater attached. Thus the same as a one wire.
 
dhcomp said:
...So here's a question. Does a 3 wire function like a 1 wire if no power is provided to it? Meaning, will it still read and provide a signal back to the computer....or does it HAVE to have that power?

I ask, because currently, mine is wired to a spare ACC ign on feed under my hood. This is all fine and dandy when the truck is running with the key in....but if i remote start it, this circuit doesn't get power.

I need to transfer the power to actual IGN power, but didn't have time.
Click to expand...


Looks like you have it wired up and good. The signal wire (odd color) is the only important one to have correct. With the other 2 wires that should be the same color, one goes to 12v, the other to ground.

Regarding your question: If you are only remote starting your motor to warm up, then you are OK with this. The O2 sensor may not function at this time w/o the 12v source, but your motor should just run in open loop until you actually turn your key.
I wired mine through a relay triggered by my fuel pump source. This way it is not constantly on if I have my key on / motor off.
 
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